Bis(tert‐butoxyaluminum dihydride) (tBuOAlH2)2 decomposes on metal surfaces heated to 250 °C (Fe, Ni, Cu, Pt) and under reduced pressures of 0.01−0.1 atm with elimination of dihydrogen and isobutene to form a glasslike, amorphous film, which is composed of equimolar parts of hydrogen, aluminum and oxygen (elemental analysis, EDX analysis). The gases eliminated during this process were characterized by mass spectroscopy (H2, isobutene) or by infrared matrix techniques (isobutene). The exclusive binding of hydrogen to aluminum is deduced from IR spectroscopy of the HAlO film and of its deuterated form DAlO. The HAlO layer (which shows no X‐ray diffraction pattern), when heated to 450 °C or when exposed to a CO2 laser, loses hydrogen and transforms to an almost stoichiometric composite with nanoscale crystalline aluminum and aluminum oxide (Al/Al2O3) as ingredients. This transformation may be followed by IR spectroscopy, by 27Al MAS NMR or by XPS, the latter showing different signals (Al, 2p electrons, Mg‐Kα, θ = 0°) for HAlO (74.2 eV) and for the composite (Al: 72.1 eV, Al2O3: 75.3 eV). Microstructures that are characterized by different chemical compositions and different optical contrasts of the “drawing”, relative to the surrounding matrix, may be generated with an X/Y‐table and a CO2 laser. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Interference of coherent laser beams may be used to structure different types of materials ranging from metals [1] over semiconductors [2,3] to organic polymers. [4] In this process coherent laser beams interfere with one and another to create perfect line-like or dot-like periodic patterns with a very high long range order. During this process the periodic energy distribution is used to be transformed by three effects according to Bäuerle: [5] In the case of polymers with a low amount of free' electrons to interact with the electrical field vector of the electromagnetic wave, primarily a non-thermal photochemical bond-breaking and resulting ablation of material gives the possibilty for a topographical structuring. In the case of semiconductors and ceramics both thermal and nonthermal effects are in an equilibrium and a photo-physical periodical ablation and periodical heat treatment with effects such as melting, re-crystallization and phase transformation, etc., are the results. In the case of metals with a large amount of free' electrons, the non-thermal wave energy is instantanaously transformed into heat and gives the possibility for a periodical heat treatment. Periodical heat treatment of ceramics and metals opens the path to periodical micro-metallurgy. [1] Recently, we have shown that a HAlO layer, which has been produced using the molecular precursor ([tBu-O-AlH 2 ] 2 ) [6,7] in a CVD (chemical vapor deposition) process, can be transformed through thermal treatment into an Al/Al 2 O 3 composite. The chemical processes in these transformations are assembled in the Reactions 1 to 3.These reactions can be explained as follows: In a first step the HAlO layer is deposited on metallic (Cu, Ni, Fe) or semiconducting (Si) substrates, when a gas flow of [(H 3 C) 3 C-OAlH 2 ] 2 at reduced pressure is oriented on the heated substrate. At temperatures over 230 C on the surface of the substrate, the molecular precursor loses simultaneously hydrogen and isobutene forming a transparent layer of HAlO. [8] When this HAlO layer is heated up to higher temperatures (400-550 C), one can observe the evolution of dihydrogen in an on-line mass spectrometer and also a steady change of the color to grey or black, depending on the conditions (time of heating, thickness of the HAlO layer). Elemental analysis (volumetric titration of the metal ions and EDX) of the obtained layer reveals a 1:1 molar ratio of aluminum and oxygen and no hydrogen due to CHN-analysis. In the X-ray diffractogram of the layer (scratched and grinded to a powder) only the diffraction lines of aluminum appear, whereas after heating in a vacuum additional lines of a second phase evolute, which can be attributed to c-Al 2 O 3 . From these findings it can be deduced that the ceramic HAlO layer has been transformed to a composite of metallic aluminum in an amorphous Al 2 O 3 matrix. 27 Al solid state NMR in the MAS mode as well as XPS spectroscopy of this composite reflect the composite nature of the product as well as of its phases. We assume that the mechanism ...

Using a CO 2 Laser. -Glass-like films of the title compound are synthesized by gas-phase decomposition of (tBuOAlH 2 ) 2 on metallic substrates heated to 240-250°C at 0.01-0.1 atm. The samples are characterized by powder XRD, IR, NMR MAS, and XPS spectroscopy. The HAlO layer, when heated to 450°C or when exposed to a CO 2 laser, transforms to an almost stoichiometric Al/Al 2 O 3 composite. Microstructures that are characterized by different chemical compositions and different optical contrasts of the "drawing", relative to the surrounding matrix, may be generated with an X/Y-table and a CO 2 laser. -(VEITH*, M.; ANDRES, K.; FABER, S.; BLIN, J.; ZIMMER, M.; WOLF, Y.; SCHNOECKEL, H.; KOEPPE, R.; DE MASI, R.; HUEFNER, S.; Eur.

The cover shows a light microscopic image of a patterned HAlO film with Al‐Al2O3 lines (dark regions). The micro‐patterning is obtained by laser interference metallurgy, and more about periodical microstructuring using laser interference metallurgy can be found in the article by Veith, Mücklich et al. on page 27.